Method and apparatus for impregnating fibrous material



Nov. 24, 1942.

B. CAMPBELL ETAL 2,303,257

METHOD AND APPARATUS FOR TMPREGNATING FIBRoUs MATERIAL Filed July 31,/1940. 3 sheets-sheet 1 uw@ lo n A@ A A M T w M\ fo m I cu n: 1*

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Or'ro Mensa' "'vp Nov. 24, 1942. B. CAMPBELL ETAL METHOD AND APPARATUS yFOR IMPREGNATING FIBROUS MATERIAL Filed July 3l, 1940 3 Sheets-Sheet 2 INVENTORS Sify/ L, J S c4 6 E M/M www H .W T c.; MA as MTW anni?. 0N m nrP urs NOV. 24, 1942. B. CAMPBELL ET A| 2,303,257

METHOD AND APPARATUS FOR IMPREGNATING FIBROUS MATERIAL Filed July 31, 1940 5 Sheets-Sheet 3 tlg/60 woo Md spx/n E RM W N O6 WR Tasa o N JJ T Ema. WM l o treating solution is always under atmospheric pressure; (2) plac- (3.) heating the the treating solution;

Patented Nov. 24, 1942 METHOD AND APPARATUS FOR IMPREG- NATINQFIBROUS MATERIAL William Boyd Campbell, Montreal, Quebec, Otto Maass, Westmount, Quebec, and Ernest Edward Massey, Montreal, Quebec,

Canada, assignol's to Imperial Tobacco Company of Canada, Limited, Montreal, Quebec, Canada Application July 31, 1940, SerialKNo. 348,962

. 11 Claims.

.This invention relates to' the production of wax impregnated cigarette paper and is a continuation, in part, of the invention set forth in our .co-pending application Serial No. 271,950, filed May 5, 1939.

The main object of the invention is to provide an eiiicient method and apparatus whereby rolls of cigarette paper may be uniformly impregnated with wax by soaking the rolls in a treating solution consisting of wax dissolved in a volatile solvent that will not swell or votherwise adversely 'affect the rolled paper. To this end the invention consists in subjecting the rolled paper to successive soakings in said solution with intermediate removal of the solvent from both the treating vessel and the paper by the application ofheat and suction, the soaking treatments befl ing carried out at a temperature above the boiling point of the solvent contained in saidy solution.

In the process described herein repetition of' the soaking-step is -a necessary and important feature since a single stage soaking, no matter how prolonged, will not give uniform and satisfactory penetration of the paper by the wax when the paper is treated in the form of rolls. Complete removal of the solvent from the paper between soaking treatments is also a vital step. in

` the absence of which repetition of vthe soaking give the desired uniform step is not effective to and satisfactory penetration.

' In its preferred application the invention comprises the'following steps: (1) introducing the into a storage chamber which ing the rolls of paper in a Vtreating chamber;

treating chamber .and its. contents to atemperature above the boiling point of the solvent contained in the treating solution; (4) placing the treating chamber in communication with a source of suction during the latter part of the heating periodV of step 3 and disrupting said communication when a predetermined sub-atmospheric pressure is established in ysaid chamber; (5) cooling the walls of said chamber to a temperature below the boilingV point of (6) placing the evacuated treating chamber in communication with the lstorage chamberso that the treating solution is transferred fromv the storage chamber to the f treating chamber by atmospheric pressure aided bythe vacuum previously established in the treating chamber; (7) disrupting the communication .between Said chambers when the transfer of the treating solution is completed; (8) permitting the rolls of paper to soak in the treating solui tion fora suitable period of time while heating the treating chamber to a temperature above the boiling point of the solvent contained in the treating'solution; (9) re-establishing communication between the treating chamber and the storage chamber whereby the unabsorbed treating solution is forced back to the storage chamber by the pressure of the evaporated' solvent contained in the treating chamber; (10) disrupting communication between said chambers when the transfer of unabsorbed treating solution fromthe treating chamber to the storage chamber is completed; (11) removing al1 solvent from the. treating chamber and from the treated material by exhausting the evaporated solvent from said chamber while simultaneously heating said .chamber to a temperature above the boiling point of the solvent. Steps 5 to 11 inclusive are4 then repeated, following which the rolls of paper are removed from the treating chamber and allowed to cool.

The treating solution is preferably heated to a temperature of about 50 to 60 C. before being run into the treating tank. Due to the low pres# sure existing in the tank when the treating solution is introduced some' of the solvent immediately volatilizes. 'I'his volatilization continues until the vapor establishes suilicient pressure to prevent further boiling or volatilization of the solution. If any temperature differences exist in the treating chamber the evaporated solvent will condense on the cooler places until equilibrium is established. Consequently, if the rolls of paper in the treating chamber are cold when come soaked by pure solvent formed-by condensation of the vapor coming in contact therewith. This, of c`o`urseprevents satisfactory penetration of the rolled paper by the treating solution. We have found thatl this difiiculty is reduced to a--minimum when .the introduction of the solution into the' treating chamber is preceded by the preliminary heating and cooling steps (steps 3 and 5) mentioned in the preceding paragraph. 'I'he result of these steps is to establish a temperature differential between the paper rolls and the Walls of the heating chamber which favors condensation on the walls rather than on the rolls and thus ensures that the solution will penetrate a greater distance inwardly from the edges toward the center of the rolled paper than wouldA otherwise be the case.

that the maximum amount of heat be applied to each paper roll to assist in the evaporation and removal of the absorbed solvent. This is accomplished by loading the. rolls on a hollow heat conducting mandrel which passes upwardly through the bobbin or central opening of each roll, suitable heat conducting spacers being arranged on the mandrel between adjacent rolls. The spacers and the bobbins of the rolls should be a snug t on the mandrel to ensure the maximum conduction of heat to the central and side portions of each roll. After the paper rolls and spacers have been secured thereon the mandrel is fitted snugly over a hollow heatable core which islocated in and forms part of the treating chamber, said core being preferably heated by means of a heating coil arranged therein.

The heat applied in step 11 serves to distill of! the solvent contained in the treating solution which penetrated or was absorbed by the paper during the preceding soaking step (step 8). This distillation of the paper absorbed solvent is accelerated by the metal heat conducting elements in contact with the paper rolls and by the reduction in pressure inthe treating chamber which is brought about byl connecting the treating chamber toa source of suction to remove the evaporated solventi`threfrom- The evaporationofthe paper absorbed solvent serves to cool down the paperrolls, the extent of the cooling being proportional to the rate of evaporation. This cooling f the paper has two effects: first, the waxes being less soluble in the cold are deposited; secondly, the solvent evaporates much more s lowly as it becomes colder.

vDuring the distillation of the solvent the pressure in the treating chamber gradually decreases as the evaporated solvent is removed. `It has been found, h owever, that thesolvent removal is not yet complete whenl the pressure gauge of the treating chamber indicates that the 4maximum vacuum has been obtained. Consequently. ln order to ensure theI reouislte complete removal of all solvent from the treating chamber andits contents, it is necessary to apply heat during theevacuation of the heating chamber in step 11. In practice it takes about one hour to reach an absolute pressure of 1/4 of mercury in the treating chamber during this step. The treating chamber is then heated for a further period of about one hour while still connected to the suction or vacuum apparatus. A

temperature of 100 C. is maintained during this time. The conditions obtaining in the treating chamber during the second soaking treatment are slightly different as compared with the conditions obtaining during the initial soaking. The solvent vapors which condense on the paper at the. beginning of the second soaking treatment will dissolve the Wax already present in the euter portions of the rolled paper strips and it is this solution, rather than pure solvent, which penetrates to the center of the rolled material as the second soaking treatment progresses to completion.

When step 11 isrepeated, the duration of the heating period following the establishment of an absolute pressure of 1A of' mercury in the treating chamber may be reduced to about 10 minutes.

Reference will now be had to the following detailed description taken in connection with the accompanying drawings, in which- Fig. 1 is a diagrammatic view, partly in section, of one form of apparatus which may be used in carrying the invention into effect. In this view the treating chamber is shown as it appears prior to the introduction of the paper rolls.

Fig. 2 is an enlarged vertical sectional view oi ranged therein.

Fig. 3 is a top plan view of one of the heat conducting spacers which are arranged on the mandrel between adjacent rolls.

Fig. 4 is a sectional view taken substantially along the line 4-4 of Fig.\3.

Fig. 5 is a sectional view of one of the heat conducting plates which are employed in conjunction with the heat conducting spacers shown in Figs. 3 and 4.

Referring more particularly to the drawings. 5 designates the treating tank in which the paper rolls are treated in accordance with this invention. The treating solution, consisting of waxes dissolved in a suitablevolatile solvent, is prepared in or introduced into the treating solution storage tank 6. In practice we prefer to prepare the solution in tank 6 by introducing the necessary ingredients through valve 1 which to one end of a condenser coil I3 arranged in condenser tank; I4. The remaining end of coil I3 is connected, through line I5, to a vacuum pump (not shown). Line I5 is provided with valves I6 and I1. This line is also provided, at opposite sides of valve I1, with branches I8 and I9 leading to a solvent tank 20. Branches I8 and I9 are provided, respectively, with valves 2I and 22. Lines I2 and I5 are also directly connected through bypass line I2a equipped with a valve I2b. Line I2 is equipped with valves I2c and I2d, the former being located between bypass connection I2a and coil I3 and the latter being located between bypass connection I2a and tank 5.

Tank 5 is provided with a water jacket 24 containing two steam heating coils 25 and 2G. Water is supplied vto and withdrawn from jacket 2l through pipe 21. A hollow heatable core 28 is centrally located in tank 5. The lower end of core 28 is open and is welded-or otherwise se- A vent pipe 3|a lalso extends upwardly within core 28.

Tank 5 is also provided with a removable top cover 33 secured in place by the swinging eye bolts 34 'and clamping nuts 35. A compressible sealing member. 31 is secured in a channel shaped holder 38 fastened to the underside of cover 33.

. When cover33 is secured in place by bolts 34 vand lifting' bail 61.

as diagrammatic-any indicated in Fig. 1, me

solution storage tank 6 is also provided with a water jacket 46 containing a steam heating coil 41, water being supplied to said jacket through pipe 48.

The rolls of paper to be treated in accordance with this invention are indicated at 50 in Fig. 2.-

These rolls are arranged, one above the other, on

y a hollow heat conducting mandrel 5| which is fitted over the heatable core 28 contained in treating tank 5. The rolls are loaded on the mandrel so that vthe latter extends upwardly through the bobbin 52 of each roll and through the central openings of suitable heat conducting spacers 53 interposed between adjacent rolls. Additional heat conducting elements are also indicated at 54 and 55, the element 54 being arranged on the'mandrel 5| in contact with the upper side of the top roll 50. and the element 56 being interposed between the lower side of the bottom roll 50 andthe hub 51a of the mandrel flange 51.

Each of the heat conducting spacers 53 comprises spaced upper and lower ring shapedplates 58 made of stainless steel; the inner circular edges of said plates being substantially flush with the inner periphery of an interposed spacing ring 58a'which surrounds the mandrel and is welded or otherwise secured to the opposing surfaces of said plates. Each plate is provided with a multiplicity of 4small openings 59 and the top plate 58 is also provided with struck outspacer tongues 80 which are bent downwardly into en-` gagementwith the bottom plate to serve as ad-A ditional spacers between theplates. Obviously. the tongues 60 may be struck from the bottom instead of the top plate 58 or they may be struck from both of said plates at suitable points.

Each of the heat-conducting elements 54 and 55 comprises a single ring shaped plate provided with a multiplicity of small openings 62 and having-its inner peripheral portion welded or otherwise secured to a spacer ring 53 surrounding the mandrel. The bobbins 52 and the heat conducting elements 53, 54 and 55 should be a snug` iii on the mandrel to ensure the maximum conduction of heat to the center and side portions of each roll. For the same reason it is desirable that the mandrel be a snug sliding'ft on the heatable t core 28, the slight clearance shown between these elements being` preferably omitted in actual -l practice.

The rolls 58 and the associated heat conductingelements 53, 54 and 55 arel lsecured'in place betwc en the manual flange hub 51a and are'mov- In this connection it will be noted that the man- I drel comprises a metal tube having its upper end closed -by an inserted plug 66 provided with a i Sleeve 65 carries a clamping screw 68 which is screwed tightly against the bottom wall of a groove 69 provided in plug 65, saidgroove registering with a screw receiving slot 10 extending downwardly from the upper end of the mandrel tube.

Paper disks (not'shown) are preferably placed between the rolls 58 andfthe heat conducting elements 53, 54 and 55to serve as filters and to assist in keeping the paper rolls cleans: 'I'he rolls 5|) and the associated heat conducting elements 53, 54 and 55 should be packed as tightly as possible on the mandrel to ensure good heat conducting contact between the heat conducting elements and the paper. In practice the rolls and associated heat conducting elements are secured in place on the mandrel before the latter is fitted over the heatable core 28.

The apparatus is'put into operation in the following manner: The treating tank 5 is loaded with the paper rolls as shown in Fig. 2 andthe treating solution .is prepared in or introduced finto tank 8. At this time valves 1, I6, I1, |2b and |2d are open but valves 2|, 22, 9 and |2c are closed. The preliminary heating of the tank (step 3) is then effected by supplying steam to` heating coil 3| contained in core 28 and to one or both of the heating coils .25 and 26 contained in the water jacket 24. The tank and its contents are thus heated to a temperature' of l-100 C. which is maintained for a period of about 55 minutes. Towardthe end of this preliminary heating period valve |2c is opened so that a vacuum is drawn on tank 5 to establish a predetermined absolute pressure therein. When this isaccomplished valve |2c is closed andthe walls ing tank 5 is now placed in communication with the storage chamber so that the treating solution is transferred from the storage chamber 5 to the treating chamber by atmospheric pressure. Valves I5 and |2d are now' closed and valve 9 is open. Since tank 6 is under atmospheric pressure (the valve 1 being still open) the solution contained therein is quickly drawn into the previously evacuated treating tank 5 through line l and valve 8. When this transfer iscompleted valve 9 is closedand the paper rolls are allowed to soak in the treating solution for a period of about 45 minutes, during which thev treating chamber is again heated to a temperature 4of about C. by the heating coils 25, 26, and 3|.

'pwing'to resulting vaporization of the solvent 'back to the storage chamber 5 by the pressu're of the evaporated solvent contained in the treat- 'chamber to a temperature above, the boiling point of the solvent. To this end a vacuum is drawn on solvent tank 20, coil I3, and line I2 by opening valves I6, I1, 2|, 22, and I2cA while valves I2b and I2d are closed. When the desired vacuum conditions are thus established in tank 20, coil I3 and line I2, the valves I6 and I1 are closed and valve I 2d is opened. At this time water from a cooling tower or other source is circulated through the condenser tank I4 by opening valve 12 in the water supply line 13 and valve 'Il in the drain line 15. vWith this particular setting ofthe valves (valves I6, I1, and I2b being closed and valves 2l. 22, I2c, and I2d being open) the evaporated solvent is drawn from treating tank 5 into the solvent tank 2.0 through line I valves I2d and I2c, condensing coil I3, line I9,

and valve 22. During this solvent evacuationstep, the temperature of tank 5 is maintained volatile solvent. However, in the application of the invention to the wax impregnation of paper, especially in roll form, it is essential that the solution used be such that it does not swell the paper or cause it to deteriorate in any material respect and the solvent employed in making up the solution should be selected accordingly Having thus described our invention, what we claim is:

1. The method of impregnating paper in the form of rolls with a treating solution which does not swell the paper which comprises (1) introducing the treating solution into a storage chamber which is always under atmospheric pressure; (2) placing the rolls of paper in a treating chamber; (3) heating the treating chamber and its contents to a temperature above the boiling point of the solvent contained in the treating solution; (4) placing the treating `chamber in communication with a source of suction during the latter part of the heating period of step 3 and disrupting said communication when a predetermined sub-atabove the 'boiling point of the solvent by the heating coils 25, 26, and 3| to ensure that all the solvent contained in the treating solution .absorbed by the paper rolls will be distilled oir and withdrawn into the solvent tank 20. The last traces of solvent are preferably removed from tank 5 by closing valve I6 and opening valve I2b to place the tank in direct communication with the. suction line I5. The operations involved in carrying out steps 5 to 11 inclusive are then repeated to ensure the desired uniform and complete penetration or coating of the paper by the wax. Following this repetition of steps 5 to 1l inclusive the paper rolls are removed from .the treating tank and allowed to stand separately in the airfor several hours to cool.

In one instance in which the invention was used forithe production of wax impregnated cigarette paper the treating solution was composed of the' following ingredients mixed together in the following proportions, by weight:

Pounds Carbon tetrachloride -150 Beeswax 2 Carnauba wax 11/2 In preparing this solution the waxes were melted and poured into the solvent which had previously been heated to 45 to'50 C. The mixture was then stirred to ensure complete solution. When any appreciable interval of time is permitted to elapse between the preparation and use of the solution it is usually necessary to reheat the solution to 45 C., since some wax may separate from the solution during such interval.

The initial heating of the solvent during the preparation of the solution, as well as any subsequent heating of the solution, may be accomplished by supplying steam to the steam-heating coil' 41 contained in the jacket 46 of the solution storage tank I5.

While the present invention is primarily concerned with the production' of wax impregnated cigarette papers and has been found peculiarly useful -in this relation, it is obvious that certain features of the invention are not limited to this application but may.also be employed in other relations where it is desirable to impregnate material with waxes or other solidsdissolved in a mospheric pressure is established in said chamber; (5) cooling the walls of said chamber 'to atemperature below the boiling point of the treating solution to establish a temperature difference which favors condensation of evaporated solvent on said walls rather than on the paper rolls when the treating solution is introduced into the treating chamber; (6) placing the evacuated treating chamber in communication with the storage chamber so that the treating solution is drawn' into the treating chamber by the vacuum previously established therein; ('1) disrupting com: munication between said chambers when the transfer of the treating solution is completed; (8) permitting the rolls of paper to soak in the treating solution for a suitable period of time while heating the treating chamber to a temperature above the boiling point of the solvent contained in the treating solution; (9) re-establishing communication between the treating chamber and the storage chamber whereby the unabsorbed treating solution is forced back to the storage chamber by the pressure of the evaporated solvent contained in the treating chamber; (l0) disrupting communication between said chambers when the transfer of unabsorbed treating solution from the treating chamber to the storage chamber is completed; (11) removing all solvent from the treating chamber and from the treated material by exhausting the evaporated solvent from said chamber while simultaneously heating said chamber to a temperature above the boiling point of the solvent: and then repeating steps 5 to 11 inclusive.

2. A method according to claim 1, in which the central and side portions of each roll are heated during steps 8 and 1l by heat conductors arranged in contact therewith.

3. A method according to claim 1, in which heat is conducted directly to each paper roll during steps 8 and 11.

4. A method according to claim 1, in which the paper rolls are arranged in the treating chamber with heat conducting spacers interposed between' paper rolls are arranged in the treating chamber in heat conducting rfb-ion with a heat conductor extending upwardly through the center of the rolls and with additional heat conductors interposed between adjacent rolls. l

7. The method ofdimpregnating material in the form of rolls which `comprises loading the rolls alternately with metallic heat conducting plates on a hollow heat conducting mandrel, iitting the mandrel over a heatable hollow core contained in the treating chamber which is closed during the impregnating operation; heating the chamber and its contents to a temperature above the boil'- ing point of the solvent contained in the treating solution, then cooling the walls of the treating chamber to below the boiling point of the solution, drawing a vacuum in the treating chamber and then placing said chamber in communication with a storage tank vin which the treating solution is maintained under atmospheric pressure whereby said solution is drawn from the storage tank to the treating cham-ber by the vacuum previously established in the treating chamber, allowing the treating solution to remain in contact with the rolls of material for a predetermined period of time during which the treating chamber is heated to a temperature above the boiling point of the solution, re-establishing communication between the treating chamber and the storage tank so that the treating solution is forced back to the storage tank by the pressure of the evaporated solvent contained in the treating chamber, disrupting communication between thetreating chamber and the storage tank when the transfer of` treating solution from the treating chamber to the storage tank is completed. and then placing said chamber in communication with a prevously evacuated condenser while heating said chamber to a temperature above the boiling point of the treating solution.

8. The 4method of impregnating paper in the form of rolls which comprises (1) introducing the treating solution into a storage chamber which is always" under atmospheric pressure; (2) placing the rolls of paper in a treating chamber; (3) heating' the treating chamber and its contents to a temperature above the boiling point of the solvent contained inV the ntreating chamber; (4) placing the treating chamber in communication with a source of suction during the latter part of the heating period of step 3 and disrupting said communication when a predetermined sub-atmospheric pressure is established in said chamber; (5) cooling the walls of said chamber to a temperature below the boiling point of the treating solution to establish a temperature difference which favors c ondensation4 of evaporated solvent on said walls l rather than on the paper rolls when the treating solution is introduced into the treating chamber; (6) placing the evacuated treating chamber in communication with the storage chamber so that the treating solution is'drawn into the treating chamber by the vacuum previously established therein; (7) disrupting communication between said chambers when the transfer of the treating solution is completed;

(8) permitting the rolls of paper to soak in the treating solution for a suitable period of time While heating the treating chamber to a tem- Vchamber to the storage chamber is completed;

(11) removing all solvent from the treating chamber andfrom the treated material by exhausting the evaporated solvent `from said chamber while simultaneously heating said chamber to a temperature above the boiling point of the solvent. I s

9. Apparatus for impregnating material in the form of rolls comprising, in combination, a treating chamber in which the rolls are soaked in the treating solution,.a hollow heat conducting core extending upwardly from the bottom wall of said chamber and a removable heat conducting mandrel in said chamber on which the rolls are arranged one above the other, said mandrel being tted on said core.

10. Apparatus for impregnating material in the form of rolls comprising, in combination, a treating chamber in which the rolls are soaked in the treating solution, a removable heat conducting mandrel in said chamber on which the rolls are arranged one above the other and heat conducting members arranged on the mandrel between adjacent rolls.

11. Apparatus for impregnating material in the form of rolls comprising, in combination, a treating chamber in which the rolls are soaked in the treating solution, and a removable heat conducting mandrel in said chamber on which the rolls are arranged one .above the other, said mandrel being equipped withclamping means for clamping the rolls in place thereon.

W. BOYD CAMPBELL. OTIO MAASS. E. EDWARD MASSEY. 

